In the conventional and most common type of disc brake arrangement as defined above a so called brake unit, i.e. a brake cylinder with built-in slack adjuster of pushing type, is arranged between the ends of two brake levers, which at their opposite ends are provided with the pad holders and at intermediate points are pivoted to and interconnected by means of a cross bar. The arrangement is suspended in a comparatively complicated way.
This arrangement is complex, heavy and costly, although for most purposes it is chosen, partly because its different parts are standardized to a certain degree and thus are interchangable.
However, there is a tendency in the rail vehicle construction industry to minimize the available space around the brake discs, which may be separate or wheel-mounted. Thus in many modern constructions a conventional disc brake arrangement as described cannot be used.
Different special disc brake arrangements aiming at obviating the problems and drawbacks dealt with above have been suggested, but they all suffer from different disadvantages.